The invention relates to a cap-free filler neck for a motor vehicle tank, the upper end of the filler neck's tubular part, which is connected to the tank, containing an insert, which insert comprises a funnel part with a throat and a partition part adjoining the throat at the bottom, wherein the upper end of the funnel part and the partition part adjoin the tubular part in a sealing manner, and wherein the partition part has a throughflow opening which is closed in a sealing manner by a flap, which can be locked in the closed position, and can be pivoted into an open position counter to the force of a spring by a fuel nozzle.
Cap-free filler necks are an attractive solution if the filler neck ends in a trough of the vehicle body, which trough, for its part, is covered by an external flap which is flush with the external contour of the vehicle. The external flap is generally lockable, but does not close tightly, and therefore rainwater may penetrate into the trough. For refueling, the external flap then only needs to be opened and the fuel nozzle to be introduced into the filler neck.
In order to prevent rainwater from penetrating into the tank, the “unleaded flap” which is already present for another purpose is of sealing and lockable design; it is unlocked when the fuel nozzle is introduced through its mouth pipe (if it has the correct diameter). The external flap and the unleaded flap make it unnecessary to have a closure cap for the end of the filling pipe, said closure cap being connectable to the latter by means of a bayonet-type fastening or thread.
Lockable (unleaded) flaps of this type are disclosed, for example, in DE 100 51 212 A1. They are attached to the inner end of a funnel-shaped insert and open inward. However, since the external flap is not watertight, rainwater can collect in and around the insert and, when the fuel nozzle is introduced, may enter the tank as soon as the fuel nozzle unlocks and opens the flap. U.S. Pat. No. 5,056,570 discloses a cap-free filler neck which has a device for the controlled conducting away of fuel vapors.